How severe is CVE-2026-5246?

CVE-2026-5246 has a CVSS 3.x base score of 5.6, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.

Is CVE-2026-5246 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-5246?

CVE-2026-5246 affects Cesanta Mongoose. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-5246?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-5246 have an EU (EUVD) identifier?

Yes. CVE-2026-5246 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18184.

When was CVE-2026-5246 published?

CVE-2026-5246 was published on 2026-04-02 and last updated on 2026-06-17.

CVE-2026-5246

CVE-2026-5246 is a medium-severity vulnerability in Cesanta Mongoose with a CVSS 3.x base score of 5.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-285.

Key facts

Severity: Medium (CVSS 3.x base score 5.6)
CVSS v2: 5.1
CVSS v4: 2.9
EPSS exploit prediction: 1% (46th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-18184
Weakness: CWE-285
Affected product: Cesanta Mongoose
Published: 2026-04-02
Last modified: 2026-06-17

Description

A vulnerability was determined in Cesanta Mongoose up to 7.20. Affected is the function mg_tls_verify_cert_signature of the file mongoose.c of the component P-384 Public Key Handler. Executing a manipulation can lead to authorization bypass. The attack can be executed remotely. Attacks of this nature are highly complex. The exploitability is told to be difficult. The exploit has been publicly disclosed and may be utilized. Upgrading to version 7.21 is able to address this issue. This patch is called 0d882f1b43ff2308b7486a56a9d60cd6dba8a3f1. The affected component should be upgraded. The vendor was contacted early, responded in a very professional manner and quickly released a fixed version of the affected product.

Frequently asked questions

What is CVE-2026-5246?: A vulnerability was determined in Cesanta Mongoose up to 7.20. Affected is the function mg_tls_verify_cert_signature of the file mongoose.c of the component P-384 Public Key Handler. Executing a manipulation can lead to authorization bypass. The attack can be executed remotely. Attacks of this nature are highly complex. The exploitability is told to be difficult. The exploit has been publicly disclosed and may be utilized. Upgrading to version 7.21 is able to address this issue. This patch is called 0d882f1b43ff2308b7486a56a9d60cd6dba8a3f1. The affected component should be upgraded. The vendor was contacted early, responded in a very professional manner and quickly released a fixed version of the affected product.
How severe is CVE-2026-5246?: CVE-2026-5246 has a CVSS 3.x base score of 5.6, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.
Is CVE-2026-5246 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-5246?: CVE-2026-5246 affects Cesanta Mongoose. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-5246?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-5246 have an EU (EUVD) identifier?: Yes. CVE-2026-5246 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18184.
When was CVE-2026-5246 published?: CVE-2026-5246 was published on 2026-04-02 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:cesanta:mongoose:*:*:*:*:*:*:*:*

More vulnerabilities in Cesanta Mongoose

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CVE-2019-19307 — Critical (CVSS 9.8): An integer overflow in parse_mqtt in mongoose.c in Cesanta Mongoose 6.16 allows an attacker to achieve remote DoS…
CVE-2019-12951 — Critical (CVSS 9.8): An issue was discovered in Mongoose before 6.15. The parse_mqtt() function in mg_mqtt.c has a critical heap-based…
CVE-2018-20356 — Critical (CVSS 9.8): An invalid read of 8 bytes due to a use-after-free vulnerability in the mg_http_free_proto_data_cgi function call in…
CVE-2018-20355 — Critical (CVSS 9.8): An invalid write of 8 bytes due to a use-after-free vulnerability in the mg_http_free_proto_data_cgi function call in…

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